Combined treatment of toxic cyanobacteria Microcystis aeruginosa with hydrogen peroxide and microcystin biodegradation agents results in quick toxins elimination

In some conditions the growth of toxic cyanobacteria must be controlled by treatment with algicidal compounds. Hydrogen peroxide has been proposed as an efficient and relatively safe chemical which can remove cyanobacteria from the environment selectively, without affecting other microorganisms. However, the uncontrolled release of secondary metabolites, including toxins may occur after such a treatment. Our proposal presented in this paper is fast biodegradation of microcystin released after cell lysis induced by hydrogen peroxide. The effectiveness of both Sphingomonas sp. and heterologously expressed MlrA enzyme in the removal of the toxin from Microcystis aeruginosa culture has been investigated. The results indicate that neither Sphingomonas cells nor MlrA are affected by hydrogen peroxide in the concentrations which stop the growth of cyanobacteria. A several-fold microcystin reduction was documented in the presence of these agents with biodegradation ability. Our results provide evidence that such a combined treatment of water reservoirs dominated by microcystin-producing cyanobacteria may be a promising alternative which allows fast elimination of toxins from the environment.